Methanol, commonly known as wood alcohol, is easily manufactured from municipal or forest wastes, coal or petroleum. In some respects methanol has been considered as a possible alternate fuel to gasoline. Like gasoline it is a liquid. There exists the technology to produce methanol from a variety of sources including coal. Methanol, however, suffers problems of poor cold weather starting, causing corrosion to engine parts and low heating value. These problems are related to methanol's similarity to water. For instance, methanol has a high heat of vaporization of 184 calories per gram. This acts to cool the intake manifold rapidly thus causing methanol to remain a liquid into the combustion chamber. By comparison, gasoline's heat of vaporization is about 80 calories per gram. Gasoline also has some very volatile (light ends) components which are easily vaporized to provide easy cool weather starting. Like water, methanol also catalyzes some corrosion reactions especially when small amounts of water are present. The heating value of methanol is less than one half of that of gasoline. This means that automobile tankage and external storage facilities would have to be more than doubled in size to be on par with present standards. Mixing methanol with gasoline to increase automobile fuel supplies has been considered. However, methanol's low solubility in gasoline especially in the presence of a small amount of water is of vital concern, and the fuel mixture becomes corrosive when methanol is added.
At approximately 500.degree. C. in the presence of a nickel (Ni) catalyst on aluminum oxide (Al.sub.2 O.sub.3) methanol (Ch.sub.3 OH) rapidly disassociates to carbon monoxide (CO) and hydrogen (H.sub.2). The equilibrium for this reaction is greater than 97% toward synthesis gas at the 500.degree. C. temperature and one MPa (10 atm). The heating value of the fuel is now increased from methanol at 4802 cal/g (8644 Btu/lb) to the synthesis gas (CO and H.sub.2) at 5693 cal/g (10,24 Btu/lb.). This is 119% of the original heating value. In essence, waste heat from the exhaust gas is used to increase the energy content of the fuel and thus increase the overall engine efficiency.
In a secondary synthesis at around the same temperature but in the presence of an iron (Fe) catalyst on Al.sub.2 O.sub.3 the CO and water (H.sub.2 O) shift to CO.sub.2 and H.sub.2. The heating value has little change, however, an improvement in pollution control results when the fuel is burned in the engine. This is due to the lower burning temperature because of the heat capacity added by the CO.sub.2 being carried into the engine which must be heated in combustion. The equilibrium for nitrous oxide formation is less at the lower combustion temperatures.
The source of heat for heating the methanol and water is the waste heat in exhaust gases. This consists of around 35% of the fuels energy. Approximately 55% of the exhaust gas' available heat is the amount required to heat the fuel for the synthesis. The hot synthesis gas heats the entering methanol and water to exchange heat which cools the synthesis gas for storage before consumption.
The engine fuel system to the combustion chamber is typically a gas fuel system such as a propane type. An alternate fuel source may be provided which typically is propane. Air typically 21% oxygen and 79% nitrogen is pumped from the ambient atmosphere to provide the oxidizer. Water may be pumped in from the water tank to reduce the combustion temperature to minimize the nitrous oxide pollutants generated.
Advantages have been claimed for the use of hydrogen in an internal combustion engine. These advantages are a low lean limit and high specific heat which lead to higher compression ratios, greater efficiency and possibly less pollution. These advantages are increased with high pressure injection into the engine. There is, however, a great disadvantage, that is, the fuel is gaseous at ambient conditions. The use of synthesis gas as a fuel will have some of the same advantages as hydrogen with the additional advantage that its source is a liquid fuel. This means that conventional automobile tankage and dispensaries may be utilized.
Greater efficiency may be attained from two sources by converting CH.sub.3 OH or other fuels to synthesis gas and using this as the engine fuel: 1. energy is added to the fuel from the sensible heat of the exhaust gases and 2. the synthesis gas itself may be burned more efficiently. Other advantages include the possibility of using non-conventional fuel sources such as fuel oil or pulverized coal to produce the synthesis gas for the internal combustion engine.